What you want is to create a container for your ad and your sidebars. So after the loop you should see a /div to close the posting container. After that, you probably see calls to your leftmenu and sidebar. Before the calls, do a div with your ad content, make your calls to the leftmenu and sidebar, then close the container with a /div. your sidebars will be inside the container and probably contain their own div's. You would control the width of the container and the sidebars using your css file.